Weighted corrosion inhibitor



United States Paten 2,822,330 WEIGHTED CORROSION INHIBITOR Olen L. Riggs, In, and DArcy Shock, Ponca City, :Okla., ;assignors to Continental Oil Company, Ponca City, Okla, a corporation of Delaware N0 Drawing. Application March 14, 1955 Serial No. 494,226

Claims. (Cl. 252-855) This invention relates to the prevention of corrosion of metal equipment in producing oil wells. More particularly, the invention relates to the protection of steel casings, steel tubing, and other metal well equipmentfrom the deleterious effects of corrosive formation liquids.

In the production of oil, corrosion of steel and other metal well equipment is caused by .the action of certain types of sulfur-bearing waters, aqueous carbonic acid, and natural brines. Corrosive sulfide brines include alkali and alkaline earth metal sulfides and hydrogen sulfide. Hydrogen sulfide and carbon dioxide are very soluble in water and brines and in addition hydrogen sulfide is soluble in petroleum oil thus forming corrosive solutions which cause deterioration of Welland surface equipment. This corrosion takes place in brines having a .pH' below about 8, which includes practically all natural well brines.

ER is common practice to introduce an inhibitor at the wellhead into the annular space between the casing and the tubing in a well extending into a producing formation. The liquid inhibitors which have been used are expected to flow to a producing zone in the well .to mix with the corrosive liquids flowing therefrom and then will flow up through the tubing to the surface.

In gas lift Wells in particular and in some pumping and flowing wells, however, a considerable column of oil and water or brine may stand in the annular space between casing and production tubing. In such wells the conventional inhibitors will be rather inelfective in extending protection from "corrosion throughout the well. We have *found that two additional requirements must be metto insure effective placement of the inhibitor. First, the density of .the inhibitor must be greater than that of the liquids contained in the annular space, and second it mustnot be appreciably soluble in oil.

It is a principal object of this invention, therefore, to

provide a method of inhibiting corrosion in producing oil wells in which the corrosion inhibitor is weighted with aliquid to make it fall more readily through any liquid column to a producing zone in a well.

A further object of "the invention isto render oil-soluble inhibitors 'sufliciently limited in solubility so as to pass readily through the oil layer floating upon 'a column of brine without appreciable dissolution by providing a liquid solubility-limiting agent and a Weighting agent in combination with the corrosion inhibitor.

Astill further objectof this invention is to provide improved weighted corrosion inhibiting compositions for use in producing -oil wells.

Other objects of the invention will appear as the descri'ptio'n proceeds.

The foregoing objects are attained by aprocess which broadly .stated comprises a method of inhibiting corrosi on "inoil wells which comprises the addition to the annular space between "the casing and the tubing of a producing oil well a 'liquid 'c'orrosion inhibiting compositio'n icomprising' an oil soluble corrosion inhibitor, an immiscibilizing agent for the corrosion inhibitor and a mutual solvent for the inhibitor and the immiscibillzing 2 agent. The mutual solvent must have a specific gravity so that the final composition has a specific gravity greater than 1.01. Based on the weight of the composition, the inhibitor, immiscibilizing agent, and solvent may vary from 20 to 70, 5 to 25, and 5 to percent respectively.

- Before proceeding with specific examples illustrating our invention it may be well to indicate in general the nature of the materials required in the process.

The oil soluble corrosion inhibitors which are useful for the practice of this invention are iron corrosion inhibitors and in general they may be of the nitrogen chain or ring type, high molecular weight carboxylic acid, sulfonic acids and various salts of these acids with alkali metals, alkaline earth metals, ammonia, amines, and alkanolarnines. Various alk'yl pyrimidines are also suitable in the process of this invention. Nitrogen ring type inhibitors may be used also. Specific nitrogen ring type inhibitors are the N-aliphatic pyrrolinediones represented by the formula:

0 where X and. Y are members from the class consisting of hydrogen, halogen, and simple hydrocarbon groups and R is an aliphatic group, such as disclosed in U. S. Patent No. 2,466,530 issued to C. M. Blair and W. F. Gross, and are available under. the brand name Kontol- 118 which has a density of 0.957 at 60 F. The aliphatic radical contains at least 7 and not more than 32 carbon atoms. The flash point, fire point, pour point, and viscosity are 165" F., .225" F., 20 F, and 477 S. S. U. at 100 F. respectively. It is soluble in oil but insoluble in water. Among the high molecular Weight carboxylic acids suitable in the process of this invention are high molecular weight polycarboxylic acids. Especially suited are polycarboxylic acids obtained by polymerization of unsaturated acids in accordance with a method such as is described in the Journal of the American Oil Chemists Society, 24, 65 (1947). Thus, raw materials containing linoleic acid on treatment by this method yield mixtures of dimers, trimers, and higher polymers of linoleic acid. Such a polymer mixture that may be utilized in the process of this invention is available commercially under the trade designation M46lR, dimer acids. It has the following properties:

Neutralequivalent 290-310 Iodine value -95 Dimer content p'ercent ca. Trimer and higher do ca. 12

Anothersuitable polymerized unsaturated acid is available commercially under the trade designation D-85 dimer acid. It has the following properties:

Acid value 94-116 Iodine value 44-50 Molecular weight ca. 750

Suitable sulfonic acids for the process of this invention include various petroleum sulfonic acids known as mahogany sulfonic acids obtained by the sulfonation of high molecular, weight petroleum fractions. Other satisfactory sulfonic acids are those obtained by the sulfonation of alkyl aromatic hydrocarbons obtained by the alkylation of aromatic hydrocarbons with alkyl alkylating agents having more than nine carbon atoms, as, for example, haloparaffing olefins as from dehydrohalogenated haloparafiins, polyolefins such polypropylene, alkylsulfates,

. aliphatic alcohols, and others. :Spec'ific suitable sulfonic acids are those obtained by sulfon'ating alkyl aromatic hydrocarbons known in the art as dodecylbenzene, postdodecylbenzene, and diwaxbenzene. Dodecylbenzene is obtainable under the trade name of Neolene 400. Physical properties of Neolene 400 are as follows:

Specific gravity at 16 C 0.8742

Average molecular Weight 232 A. S. T. M., .D-158 Engler:

I. B. P F 535 5 F 545 F 550 50 F 560 90 F 580 97 F 592 F. B. P F 603 Refractive index at C 1.4885 Viscosity at 20 C 14 Bromine number 0.16

Postdodecylbenzene is a mixture of monoalkylbenzene and dialkylbenzenes in the approximate ratio of 2:3. Its typical physical properties are as follows:

Specific gravity at 38 C 0.8649

Although the sulfonic acids may be used, the salts formed by neutralizing these acids with alkaline materials are preferred. As stated above, about 20 to 70 percent or even less corrosion inhibitor may be present in the liquid corrosion inhibiting composition for use in oil wells and inhibition of corrosion be obtained, it is desirable that the concentration be about 50 to 70 percent in order for maximum inhibition of corrosion.

Suitable solvents for use in the process of this invention are inert solvents which have a boiling point sufficiently high that they will not boil at the temperature and pressure encountered in the well bore. As mentioned above, they should have a specific gravity sutficiently high that when they are added to the inhibitor composition the resultant specific gravity of the mixture will be greater than 1.01 preferably greater than 1.05. In general the solvent will have a specific gravity greater than 1.1. Although unhalogenated compounds satisfying the above requirements may be used, preferred solvents are halogenated hydrocarbons including, for example, the following: Monochlorobenzene, dichlorobenzene, trichlorobenzene, methylene chloride, chloroform, carbon tetrachloride, the dichloroethanes, the trichloroethanes, trichloroethylenes, the chloro and polychloropropanes, the chloro and polychlorobutanes, and the chloro and p'olychloro derivatives of higher members of this homologous series. Other suitable solvents include cyclohexyl chloride and methyl chloroacetate. The amount of solvent used in the liquid corrosion inhibiting composition for use in oil wells may be varied from 5 percent or less to about 75 percent. The minimum amount of solvent that may be used is that amount which will bring the specific gravity of the composition to at least 1.01. A greater amount of solvent would be used to reduce viscosity of the composition where viscous inhibitors and/ or immiscibilizing agents are used to that viscosity at which the composition will flow to the 4 bottom of the well. Also, more solvent would be used in the composition where the atmospheric temperatures are low in order that the composition may be readily transferred by pouring.

The immiscibilizing agent is a nonionic surface active compound soluble in the mixture of corrosion inhibiting compound and solvent and which agent by reason of its hydrophylic nature reduces the solubility of the liquid corrosion inhibiting composition in petroleum oil and which agent assists in the dispersion of the corrosion inhibiting compound under the turbulent conditions at the bottom of the well. Nonionics that may be used are those having certain definite balance between the hydrophylic and lipophylic portion of the molecule. This balance may be expressed by the HLB value of the molecule which may be determined in accordance with the methods taught by W. C. Griffin in Journal of Cosmetic Chemists, vol. II, No. 4, 1954. Thus:

where HLB=hydrophilelipophile balance S=saponification number of the nonionic A=acid number of the fatty acid portion of the nonionic,

E H LB Where:

E=weight percentage of the hydrophilic portion of the nonionic.

Noni-onics that may be used in the process of this invention have HLB values of from 10 to 17, however, the preferred range is from 13.5 to 15.5. To obtain this range of HLB values the hydrophilic portion of the nonionic molecule may be from 50 to percent of the nonionic molecule.

Different types of nonionic surface active compounds that may be used are as follows:

Prepared in Accordance with U. S. Patent Type of N onionic Compound:

1. Polyoxyalkylene ethers of fatty alcohols. 21 1934 2,425,755, Roberts, August 19, 1947.

2,41%?8139, Fife et al., December 28,

2,542,697, Nevison et al., February 2,559,583, Barker, July 10, 1951. 2,422,486, Johnston, June 17, 1947.

{1,970,578, Schoeller at 211., August 2. Polyoxyalkylene esters of fatty acids.

3. Polyoxyalkylene ethers of polyhygrsoxy alkyl esters of fatty acl Phemls' 2,522,417, Harris, September 12,

1,970,573. 4. Polyoxyalkylene ethers ofalkyl 'gg g schoeuet et June above list and having HLB values in the preferred range for use in the process of this invention are known 'by their trade names as Atlas G-1441, Atlas G-2079, Atlas G-2144, Atlas G-3720, Atlas G-3915, Atlas G3920, Tweens 60, 65, 80, and 85.

aheaeeo Atlas 6-1441 is a pelyoxyethylene soi-bit'ol lanolin eerivative having an HLB value of 14.

Atlas G-2079 is .a.polyoxyethylehe monop'almitatehaving an HLB value of 15.5 and ta general formula:

' 3T 2) t where x=about 20. i l v Atlas G--2144 is a polyoxyethylene mono-oleate having anyI-ILB value of 15.1 and a general formula:

Atlas 6-5720 is a polyqxyethylene monostearyl ether having an HLB value of 15.3 and a general formula:

Atlas 6-3915 and Atlas 6-3920 are polyoxyethylene monooleyl ethers having HLB values of 1553 and 15.4, respectively, and the general formula;

Tween 60 is a elyexyethylene sorbitan moiio'stearate having an value of 14.9 and the general formula: CH3 (CH COO=C H O ==(CH CH O) 5H where x=about 15.5. I

Tween 65 is a polyoxyethylene sorbitan tnstearate'having an HLB value of 10.5 .and a general formula:

(CH (CH CO'O) C H1O (CHCH D) H where x=about 18.

6 mild carbon steel test coupon subject to eorresiencon di'tio'ns in the presence of p. p. m. of inhibitor composition by comparing the Weight loss of a similar test coupon when subject to corrosion conditions in thefabsence of the inhibitor composition. A large mouthed:- tle of about 250 ml. capacity was charged with 150 ml. of Arbuckle brine and 50 m1. of Arbuckle oil containing the corrosion inhibitor composition being tested. The bottle was agitated to distribute the corrosion inhibitor between the two phases, a weighed 1-inch by 3-inch 10-20 mild carbon steel coupon inserted, and the bottle stopper fitted on. Carbon dioxide was bubbled through the solution at a rate of about 12 ml. per second. After about 160 hours, the coupon was removed from the bottle, d'escaled by scrubbing with a nylon bristle brush and a cleaning powder, Weighed and its loss inweight determined. The same technique was followed to obtain "a blank in the absence of corrosion inhibitor. The percent protection was calculated as follows:

P. C. P.- (Wb Wb]) x100 where:

P. C. P.=Percent protection aflorded by inhibitor.

Wbr lnitial weight of coupon subjected to test in the absence of inhibitor.

Wb =Final weight of coupon subjected to test in the ab sence of inhibitor. 7 v

Wc =lnitial weight of coupon subjected to test in the presence of inhibitor.

Wc Final weight of coupon subjected to test in the presence of inhibitor.

Protection zzfiorded by various inhibitor compositions [50 p. p. m. corrosion inhibiting composition in 3 parts of Arbuckle brine and 1 part of Arbuckle oil and a carbon dioxide environment for 160 hours] Corrosion Inhibiting Composition Experiment No.

Corrosion inhibitor Parts Per 100 Parts of Composition Parts Per 100 Parts of Percent Prote'etion Immiscibilizing Agent Solvent Tween 80.

Tween Tween Tween 60- 1 Sodium postdodecylbenzene sulfonate. 1 Postdodeeylbenzene sultonie acid.

EXAMPLE 1 The efficiencies of the various corrosion inhibitors were compared by determining the percent protection given a EXAMPLE 2 Example 1 was repeated with the exception a hydrogen sulfide environment was maintained for hours rather than a carbon dioxide environment. The results obtained were very similar to those obtained in Example 1.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto since many modifications may be made, and it is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

1. A method of treating oil wells containing a column of corrosive formation liquids which comprises the addition thereto of a weighted corrosion inhibiting composition, said composition comprising an oil soluble iron 7 corrosion inhibitor, an oil immiscibilizing agent for said corrosion inhibitor said immiscibilizing agent is a nonionic surface active compound having a hydrophile-lipophile balance (HLB) value of from 10 to 17 as determined by the following formula:

wherein S=saponification number of the nonionic A=acid number of the fatty acid portion of the nonionic and a mutual solvent having a specific gravity of more than 1.1 for said inhibitor and said immiscibilizing agent in an amount suflicient to increase the specific gravity of the inhibitor composition above that of the corrosive liquids to enable the inhibitor composition to fall readily through the liquid column to the producing zone and diffuse at least partially throughout said liquid column.

2. The method of claim 1 wherein the amount of said iron corrosion inhibitor, said oil immiscibilizing agent and said mutual solvent based upon the total weight of the corrosion inhibiting composition varies from 20 to 70 percent, 5 to percent, and 5 to 75 percent respectively.

3. The method of claim 1 wherein the amount of said iron corrosion inhibitor, said oil immiscibilizing agent and said mutual solvent based upon the total Weight of the corrosion inhibiting composition varies from to percent, 5 to 25 percent, and 5 to percent respectively.

4. The method of claim 1 wherein said immiscibilizing agent is a nonionic surface active compound having a hydrophile-lipophile balance within the range of 13.5 to

5. The method of claim 1 wherein the immiscibilizing agent is a polyoxyethylene sorbitan mono-oleate.

6. The method of claim 1 wherein the immiscibilizing agent is a polyoxyethylene sorbitan monostearate.

7. The method of claim 1 wherein the oil soluble iron corrosion inhibitor is a polymerized unsaturated acid having the following properties: acid value 94-116, iodine value 44-50, and molecular Weight ca. 750.

8. The method of claim 1 wherein the oil soluble iron corrosion inhibitor is a polymerized unsaturated acid having the following properties: neutral equivalent 290-310, iodine value -95, dimer content ca. and trimer and higher content ca. 12%.

9. The method of claim 1 wherein the oil soluble iron corrosion inhibitor is sodium postdodecylbenzene sulfonate wherein said sodium postdodecylbenzene sulfonate is the sodium salt of the sulfonic acid produced by sulnating a mixture of monoalkylbenzene and dialkylbenzenes in the approximate ratio of 2:3 having the following physical properties:

Specific gravity at 38 C 0.8649 Average molecular Weight 365 Percent sulfonamhle 88 A. S. T. M., .D158 Engler:

I. B. P F 647 5 F 682 50 F..- 715 90 F 760 F 775 F. B. P F 779 Refractive index at 23 C 1.4900 Viscosity at:

10" C centipoises 2800 20 C do 280 40 C do 78 80 C do 18 Aniline p int C 69 Pour point F 25 10. The method of claim 1 wherein the oil soluble iron corrosion inhibitor is calcium postdodecylbenzene sulfonate wherein said calcium postdodecylbenzene sulfonate is the calcium salt of the sulfonic acid produced by sulfonating a mixture of monoalkylbenzene and dialkylbenzenes in the approximate ratio of 2:3 having the following physical properties:

References Cited in the file of this patent UNITED STATES PATENTS 2,466,530 Blair et a1 Apr. 5, 1949 2,649,415 Sundberg et a1. Aug. 18, 1953 2,671,757 Wisherd Mar. 9, 1954 

1. A METHOD OF TREATING OIL WELLS CONTAINING A COLUMN OF CORROSIVE FORMATION LIQUIDS WHICH COMPRISES THE ADDITION THERETO OF A WEIGHTED CORROSION INHIBITING COMPOSITION, SAID COMPOSITION COMPRISING AN OIL SOLUBLE IRON CORROSION INHIBITOR, AN OIL IMMISCIBILIZING AGENT FOR SAID CORROSION INHIBITOR SAID IMMISCIBILIZING AGENT IS A NONIONIC SURFACE ACTIVE COMPOUND HAVING A HYDROPHILE-LIPOPHILE BALANCE (HLB) ALUE OF FROM 10 TO 17 AS DETERMINED BY THE FOLLOWING FORMULA: 